High frequency fluid cooled thermionic valve system



April 28, 1936. Q 5 K N ET AL 2,039,160 7 HIGH FREQUENCY FLUID COOLEDTHERMIONIC VALVE SYSTEM Filed Oct. 2'7, 1935 L/QU/D C0 OLEO Ali/00E aw/0COOLEO f I V 70 54/3779 70 45771 HE A PPARA 70.)

7'0 A579 INVENTORS C/MALES s. f-WAA/KL/N ATTORNEY Patented Apr. 28, 1936UNITED STATES PATENT OFFICE HIGH FREQUENCY FLUID COOLED THERMIONIC VALVESYSTEM tion of Delaware Application October 27, 1933, Serial No. 695,544In Great Britain November 9, 1932 9 Claims.

This invention relates to arrangements wherein a cooling liquid isrequired to be conveyed to and from a device which is at a point of highfrequency potential, such for example, as high frequency liquid cooledthermionic valve arrangements suitable for use in radio and similar highfrequency generating systems. An important application of the inventionis to high power high frequency thermionic valve arrangements of the Tkind in which one or more valve electrodes is cooled by means of liquid,generally water, though the invention is applicable to cases where otherstructures at high frequency potentials are required to be liquidcooled. 115 The invention will be further understood by referring to theaccompanying drawing, in which Fig. 1 is an elevation of a double woundhelix of rubber hose;

Fig. 2 is also an elevation of a double wound helix of rubber hose, andis similar to Fig. 1, ex-

cept for the addition of a conducting shield;

' Fig. 3 is an elevation of a double wound helix of rubber hose which issurrounded by a plurality of conducting rings and insulating spacingmembers which are alternately assembled around the double helix ofrubber hose. A portion of the rings and spacing members is shown insection.

As is well known it is practically necessary in high power highfrequency radio and like transmitters to cool a valve electrode orelectrodes by means of a liquid, generally water, and this is"customarily accomplished by employing ther- 'mionic valve structureswherein the anode forms 5 part of the envelope and is cooled by passingcooling liquid, generally Water, around the out side thereof, the saidcooling liquid being led to and from the valve or valves throughsuitable pipes e. g. rubber hose. As is Well known the efficiency ofsuch a liquid cooled high frequency arrangement is liable to beseriously lowered by reason of high frequency losses occurring in thecooling medium or in the hose or the supporting structure carrying thesame. For example, con- 5 sider the usual case illustrated in theaccompanying Figure 1, in which the anode of a thermionic valve (notshown) (or other apparatus at high frequency potential) is'cooled bywater led to and from it by means of a double wound helix of 50 rubberhose l, the said hose being supported by a central structure 2 aboutwhich the turns of the hose lie; in such an arrangement one end (the endA) of the coiled hose structure will be subjected to a steady directcurrent potential, and 55 also to high frequency alternating potential,the

other end (the end B) being substantially at earth potential, and, owingto self-capacity effects, the high frequency potential will fall rapidlyin the first few turns of the hose so that for these turns there will besteep high frequency 5 voltage gradients with consequent largedi-electric losses in the cooling fluid, the hose and the supportingstructure. Various expedients have been devised to meet this well knowndifiiculty and the present invention has for its object to 10 provide animproved simple and satisfactory arrangement for meeting the saiddifliculty.

According to the main feature of this invention the upper end A of thecooling liquid piping system which is subjected to high frequency al- 16ternating current potentials is enclosed in or surrounded by aconducting shield (i. e. with what may be termed a corona ring) which iselectrically connected to the source of said potential. In this way thehigh frequency potential gra- 0 dients are reduced and therefore alsothe dielectric losses in the cooling liquid, hose and supportingstructure.

In one form of construction in accordance with the invention andillustrated in the accompanying Figure 2, the conducting shield isactually in the form of a corona ring structure 3 which is well knownper se in high voltage electrical power transmission systems, and thesupport 2 about which the rubber hose or other piping is coiled is alsoutilized to carry the corona ring structure '3. Connection from thesource of highfrequency potentials to the ring structure 3 is made viathe lead 4.

The invention also envisages meeting the afore- 3,5 mentioned difiicultyby means of a special and simple constructional arrangement inaccordance with the general principles set forth in U. S. patentapplication, Serial No. 586,369, filed Jan. 13, 1932, wherein isdescribed an arrangement in 40 which a capacity potentiometer isemployed in effective parallel with the liquid carrying piping, tappingsupon the potentiometer being utilized to determine and thus to reducethe high frequency voltage gradient down the piping. The particularconstruction embodying this principle and proposed by the presentinvention is illustrated (partly in section) in the accompanying Figure3 from which it will be seen that the coil of liquid carrying piping Iis surrounded by a series of washer shaped conducting rings, said rings5 closely surrounding the coil and being insulated therefrom, said ringsbeing side by side along the length of the coil. Consecutive rings areinsulated from each other by means of spacing or 5 interposed rings 6 ofmica, or other di-electric. The ring which surrounds the high frequencyhigh potential end (A) of the coil of piping is connected via a lead Ito the source of high frequency apparatus supplying the high frequencypotential, i. e. to the same point to which the piping supplies fluid tothe anode of a thermionic valve while the ring surrounding the other endof the coil is connected to earth via a lead 8. The high frequencyvoltage gradient down the piping is determined and reduced by capacitycoupling from the potentiometer.

Having now particularly described and ascertained the nature of our saidinvention and in what manner the same is to be performed, we declarethat what we claim is:

1. An arrangement wheerin apparatus at high frequency alternatingcurrent potential is cooled by a cooling liquid comprising a pipingsystem, characterized in that that end of the cooling liquid pipingsystem which is subjected to high frequency alternating currentpotentials is surrounded by a conducting shield which is electricallyconnected to the source of high frequency alternating currentpotentials.

2. A high frequency liquid cooled thermionic valve arrangement suitablefor use in radio high frequency generating systems, and wherein valveelectrodes of apparatus operated at high frequency alternating currentpotential are cooled by a cooling liquid comprising a piping system,characterized in that that end of the cooling liquid piping system whichis subjected to high frequency alternating current potentials issurrounded by a conducting shield which is electrically connected to thesource of high frequency alternating current potentials.

3. In combination a thermionic valve having a liquid cooled anode, apiping system in the form of a double wound helix the pipes at one endof which feed cooling liquid to and from said anode and the pipes at theother end of which communicate with a source of liquid supply atsubstantially earth potential, comprising a piping system characterizedin that the end of the double Wound helix adjacent (as regards theliquid flow) the anode is surrounded by a corona ring structure which iselectrically connected to said anode.

4. An arrangement wherein apparatus at high frequency alternatingcurrent potential is cooled by cooling liquid comprising a pipingsystem, characterized in that the said piping system is surrounded by aseries of washer-shaped conductive rings closely surrounding the coil,insulated therefrom, and arranged side by side along the length thereof,said conductive rings being assembled alternating with interposed ringsof di-electric material, the end conductive ring surrounding the highfrequency potential end of the piping system being connected to thesource of high frequency potential and the other and conductive ringbeing connected to earth.

5. A high frequency liquid cooled thermionic valve arrangement for usein radio high frequency generating systems and wherein valve electrodesof apparatus operated at high alternative current potential is cooled bycooling liquid comprising a piping system, characterized in that thesaid piping system is surrounded by a series of washer-shaped conductiverings closely surrounding the coil insulated therefrom and arranged sideby side along the length thereof, said conductive rings alternating withinterposed rings of di-electric material, the end conductive ringsurrounding the high frequency potential end of the piping system beingconnected to the source of high frequency potential and the other endconductive ring being connected to earth.

6. In combination a thermionic valve having a liquid cooled anode, apiping system in the form of a double wound helix the pipes at one endof which feed cooling liquid to and from said anode and the pipes at theother end of which communicate with a source of liquid supply at orsubstantially at earth potential, characterized in that the coil ofliquid carrying piping is surrounded by a series of washer-shapedconductive rings closely surrounding the coil, insulated therefrom, andarranged side by side along the length thereof, said conductive ringsalternating with interposed rings of di-electric material, the endconductive ring surrounding the high frequency high potential end of thecoil of piping being connected to the source of high frequency potentialand the other end conductive ring being connected to earth,substantially as described.

7. A high-frequency liquid cooled thermionic valve arrangement for usein a high-frequency generating system, wherein at least one of saidvalves is cooled by a liquid comprising a piping system assembled in ahelical coil-like arrangement, one end of said piping system connectedto a source of high-frequency potential, the other end of said pipingsystem being connected to earth, and a corona ring located at the top ofsaid helical coil-like arrangement.

8. A high-frequency liquid cooled thermionic valve arrangement for usein a high-frequency generating system, wherein at least one of saidvalves is cooled by a liquid comprising a piping system assembled in ahelical coil-like arrangement, one end of said piping system connectedto a source of high frequency potential, the other end of said pipingsystem being connected to earth, a plurality of metallic rings andinsulating spacing members alternately assembled to reduce dielectriclosses in the cooling liquid flowing in said helical coil-likearrangement.

9. A high-frequency liquid cooled thermionic valve arrangement for usein a high-frequency generating system, wherein at least one of saidvalves is cooled by a liquid comprising a piping system assembled in ahelical coil-like arrangement, one end of said piping system connectedto a source of high-frequency potential, the other end of said pipingsystem being connected to earth, a plurality of metallic rings andinsulating spacing members alternately assembled to reduce dielectriclosses in the cooling liquid flowing in said helical coil-likearrangement, the diameter of said metallic rings and said spaced membersgradually decreasing toward the top of said helical coil-likearrangement.

CHARLES SAMUEL FRANKLIN. ERNEST GREEN.

